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- <th colspan="3" align="center" id="chaptername">7. Layers</th>
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- <th width="60%" align="center" id="sectionname">7.4. Mask</th>
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- <div class="sect2" lang="en" xml:lang="en">
- <div class="titlepage">
- <div>
- <div>
- <h3 class="title"><a id="gimp-layer-mask-menu"></a>7.4. Mask</h3>
- </div>
- </div>
- </div>
- <div class="informalfigure">
- <div class="mediaobject">
- <img src="../images/menus/menus-layer-mask.png" />
- <div class="caption">
- <p>
- The Mask submenu of the Layers menu
- </p>
- </div>
- </div>
- </div>
- <p>
- The Mask submenu of the Layers menu contains operations that
- involve a layer mask: creating one, applying one, deleting one,
- or converting one into a selection. See the <a href="ch04s02s03.html" title="2.3. Layer masks">Layer Masks</a> section for more
- information on layer masks and how to use them.
- </p>
- <div class="simplesect" lang="en" xml:lang="en">
- <div class="titlepage">
- <div>
- <div>
- <h4 class="title"><a id="gimp-layer-mask-add"></a>Add Layer Mask</h4>
- </div>
- </div>
- </div>
- <div class="informalfigure">
- <div class="mediaobject">
- <img src="../images/menus/dialogs-add-layer-mask.png" />
- <div class="caption">
- <p>
- The "Add Layer Mask" dialog
- </p>
- </div>
- </div>
- </div>
- <p>
- This command can be accessed from an image menubar as
- <span class="guimenu">Layer</span>-><span class="guisubmenu">Mask</span>-><span class="guimenuitem">Add Layer Mask</span>
- or from the pop-menu you get by right clicking on the active layer in
- the Layer Dialog.
- </p>
- <p>
- "Add Layer Mask" adds a mask to the layer, bringing up a dialog
- in which you can set the initial properties of the mask. If the
- layer already has a layer mask, or cannot have one because it
- lacks an alpha channel, the menu entry is insensitive. See the
- <a href="ch04s02s03.html" title="2.3. Layer masks">Layer Mask</a> section for
- more information.
- </p>
- <p>
- The popup dialog allows you six choices for the initial contents
- of the layer mask:
- </p>
- <div class="variablelist">
- <dl>
- <dt>
- <span class="term">White</span>
- </dt>
- <dd>
- <p>
- This option will produce full opacity when the layer mask;
- that is, it will be as if there were no layer mask.
- </p>
- </dd>
- <dt>
- <span class="term">Black</span>
- </dt>
- <dd>
- <p>
- This option will produce complete transparency, so that you
- will need to paint on the layer mask in order to make any
- part of the layer visible.
- </p>
- </dd>
- <dt>
- <span class="term">Layer's alpha channel</span>
- </dt>
- <dd>
- <p>
- This option will cause the layer mask to
- produce the same transparency that is produced by the
- layer's alpha channel. Note that the alpha channel itself
- will not be altered, so for partially transparent areas, the
- transparency will be "squared", as it were.
- </p>
- </dd>
- <dt>
- <span class="term">Transfer layer's alpha channel</span>
- </dt>
- <dd>
- <p>
- This option does the same thing as the previous option,
- except that it also resets the layer's alpha channel to full
- opacity. The effect, then, is to transfer the transparency
- information from the alpha channel to the layer mask,
- leaving the layer with the same appearance as before.
- </p>
- </dd>
- <dt>
- <span class="term">Selection</span>
- </dt>
- <dd>
- <p>
- This option converts the selection into a layer mask, so
- that selected areas are opaque, and unselected areas are
- transparent. If any areas are partially selected, toggling
- the <a href="ch02s04s02.html" title="4.2. QuickMask">QuickMask
- button</a> will help you predict what the effects are
- going to be.
- </p>
- </dd>
- <dt>
- <span class="term">Grayscale copy of layer</span>
- </dt>
- <dd>
- <p>
- This option converts the layer itself into a layer mask. It
- is mainly useful when you plan to add new contents to the
- layer afterwards.
- </p>
- </dd>
- </dl>
- </div>
- <p>
- When you click on "OK" the mask symbol appears at the right of the
- layer thumbnail in the Layer Dialog.
- </p>
- <p>
- If you check "Invert Mask" at the bottom of the dialog, then the
- resulting mask is inverted, so that transparent becomes opaque
- and vice versa.
- </p>
- </div>
- <div class="simplesect" lang="en" xml:lang="en">
- <div class="titlepage">
- <div>
- <div>
- <h4 class="title"><a id="gimp-layer-mask-apply"></a>Apply Layer Mask</h4>
- </div>
- </div>
- </div>
- <p>
- This command can be accessed from an image menubar as
- <span class="guimenu">Layer</span>-><span class="guisubmenu">Mask</span>-><span class="guimenuitem">Apply Layer Mask</span>.
- or from the pop-menu you get by right clicking on the active layer in
- the Layer Dialog.
- </p>
- <p>
- "Apply Layer Mask" causes the layer mask to be merged with the active
- layer, with the transparency set by the mask applied to the
- layer's alpha channel. The layer mask is removed. If the
- active layer does not have a layer mask, the menu entry is
- insensitive. See the
- <a href="ch04s02s03.html" title="2.3. Layer masks">Layer Masks</a> section for more
- information.
- </p>
- </div>
- <div class="simplesect" lang="en" xml:lang="en">
- <div class="titlepage">
- <div>
- <div>
- <h4 class="title"><a id="gimp-layer-mask-delete"></a>Delete Layer Mask</h4>
- </div>
- </div>
- </div>
- <p>
- This command can be accessed from an image menubar as
- <span class="guimenu">Layer</span>-><span class="guisubmenu">Mask</span>-><span class="guimenuitem">Delete Layer Mask</span>
- or from the pop-menu you get by right clicking on the active layer in
- the Layer Dialog.
- </p>
- <p>
- "Delete Layer Mask" deletes the active layer's layer mask. If
- the active
- layer does not have one, the menu entry is insensitive.
- </p>
- </div>
- <div class="simplesect" lang="en" xml:lang="en">
- <div class="titlepage">
- <div>
- <div>
- <h4 class="title"><a id="gimp-layer-mask-selection-replace"></a>Mask to Selection (or Add; Subtract; Intersect)</h4>
- </div>
- </div>
- </div>
- <a id="gimp-layer-mask-selection-add"></a>
- <a id="gimp-layer-mask-selection-subtract"></a>
- <a id="gimp-layer-mask-selection-intersect"></a>
- <p>
- These commands can be accessed from an image menubar as
- <span class="guimenu">Layer</span>-><span class="guisubmenu">Mask</span>,
- followed by <span class="guimenuitem">Mask to Selection</span>,
- <span class="guimenuitem">Add to Selection</span>,
- <span class="guimenuitem">Subtract from Selection</span>, or
- <span class="guimenuitem">Intersection with Selection</span>
- or from the pop-menu you get by right clicking on the active layer in
- Layer Dialog.
- </p>
- <p>
- "Mask to Selection" transforms the active layer's layer mask
- into a selection mask, that is, into the image's selection. White
- areas of the mask become completely selected, black areas
- unselected, and gray areas partially selected. The other
- operations in this group do similar things, except that instead
- of completely replacing the existing selection with the
- selection produced from the layer mask, they either add the two
- selections, subtract the layer mask selection from the existing
- selection, or yield a selection that is the intersection of the
- two. The mask is not deleted.
- </p>
- </div>
- </div>
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